Advancements in communication technologies have resulted in the development and deployment of improved communication systems through which to communicate to effectuate communication services.
In general, the communication service is effectuated by, or between, a set of communication stations that are operable in, and form part of, the communication system. The communication stations variously form sending stations that send communication data and receiving stations that receive communication data. The communication stations that are parties to a communication session, pursuant to which a communication service is effectuated, are interconnected by way of a communication channel. Communication data sent by a sending station is communicated upon the communication channel for delivery to a receiving station.
Some communication systems provide for two-way communications in which a single communication station is capable both of sending communication data and of receiving communication data.
When the communication channels used to communicate the communication data is formed of a radio channel, the communication system is referred to as a radio communication system. A radio communication system advantageously provides for communications even when communication stations operable therein are unable to be interconnected by way of wirelines upon which communication channels are defined in wireline communication systems. Free of the need to interconnect the communication devices with wireline connections, communication stations of a radio communication system are positionable at locations between which wireline connections are unavailable while still permitting communications to be effectuated therethrough. Additionally, free of the need to interconnect the communication stations with wireline connections, one, or more, of the communication stations between which data is communicated is permitted mobility, thereby permitting the radio communication system to be implemented as a mobile communication system.
A cellular communication system is exemplary of a mobile communication system. The network infrastructures of various types of cellular communication systems have been installed over significant portions of the populated areas of the world. And, their use by way of which to effectuate various communications services is widespread. Typically, users communicate through the use of mobile stations that are radio transceivers operable to transceive communication data with structure of the network of a cellular communication system in which the mobile station is operable. The networks of cellular communication systems include fixed-site transceiver stations, sometimes referred to as base stations, with which the mobile stations communicate by way of radio channels. As a mobile station travels through a geographical area encompassed by the network of a system, the communications with the mobile station are handed-off between successive ones of the fixed-site stations.
Other radio communication systems have been developed that include some of the characteristics of cellular communication systems. For instance, wireless local area networks (WLANs) include, typically, network infrastructures having fixed-site transceivers stations with which mobile stations communicate and between which communication hand-offs are performed as a mobile station travels through an area encompassed by such networks. The fixed-site transceivers of a wireless local area network are sometimes referred to as access points (APs). The hand-off of communications between successive access points of a wireless local area network permit continued communications, e.g., as a mobile station travels between coverage areas defined by the separate ones of the access points. A hand-off of communications is sometimes also referred to as a transition of communications.
In any communication service, and particularly in real-time services, e.g., voice services, communication delays when the communications are handed-off between fixed-site stations should be minimal. Otherwise, the interruption is noticeable, causing communication degradation or interruption. Proposals for standardization of hand-off, i.e., BSS (Base Station System) transition, in IEEE 802.11-compliant, and variants thereof, are undergoing consideration, and additional schemes are being proposed.
The procedures are generally categorized as being of either of two types, either a make-before-break (MBB) or a break-before-make (BBM) procedure.
In a make-before-break procedure, generally, upon determination of the need for a transition of communication from a first fixed-site station to a second fixed-site station, the mobile station performs a set of procedures, e.g., authentication procedures, with a target fixed-site station, i.e., a new access point (nAP) prior to transitioning communications from the active fixed-site station, i.e., the old access point (oAP) to the target station. By performing the procedures prior to transitioning to the target station, breaks in communications are minimized.
In a break-before-make scheme, upon determination of the need for a transition of communications to the target station, the mobile station transitions out of communications with the active station and connects to the target station.
Existing procedures include the use of pre-keying. However, the existing procedures that provide pre-keying generally require full four-way hand shake procedures to be performed pursuant to the hand-off of communications between fixed-site stations. The four-way hand shake procedure is time consuming and requires substantial overhead signaling. And, when pre-keying is performed with more than one target fixed-site station, the overhead signaling and time requirements further increase. Existing, alternative schemes of the break-before-make utilize post-keying procedures. But, in these procedures, significant time delays result due to the need to establish keys subsequent to the communication break.
In short, existing procedures and proposals are unduly time consuming and signaling-overhead consumptive. A scheme by which better to facilitate communication hand-offs would be advantageous.
It is in light of this background information related to communications in a radio communication system that the significant improvements of the present invention have evolved.